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    <pre><code>class Application { protected static $_singletonFoo=NULL; public static function foo() { if(NULL === self::$_singletonFoo) { self::$_singletonFoo = new Foo; } return self::$_singletonFoo; } } </code></pre> <p>This is the way I'd do it. It creates the object on demand:</p> <pre><code>Application::foo()-&gt;bar(); </code></pre> <p>It's the way I am doing it, it respects OOP principles, it's less code than how you're doing it right now,and the object is created only when the code needs it for the first time.</p> <p><strong>Note</strong>: what I've presented is not even a real singleton pattern. A singleton would allow only one instance of itself by defining the constructor (Foo::__constructor()) as private. It is only a "global" variable available to all "Application" instances. That's why I think its use is valid as it does NOT disregard good OOP principles. Of course, as anything in the world, this "pattern" should not be overused either!</p> <p>I've seen this being used in many PHP frameworks, Zend Framework and Yii among them. And you should use a framework. I'm not going to tell you which one.</p> <p><strong>Addendum</strong> For the ones among you worrying about <a href="http://en.wikipedia.org/wiki/Test-driven_development" rel="nofollow noreferrer">TDD</a>, you can still make up some wiring to dependency-inject it. It could look like this:</p> <pre><code>class Application { protected static $_singletonFoo=NULL; protected static $_helperName = 'Foo'; public static function setDefaultHelperName($helperName='Foo') { if(is_string($helperName)) { self::$_helperName = $helperName; } elseif(is_object($helperName)) { self::$_singletonFoo = $helperName; } else { return FALSE; } return TRUE; } public static function foo() { if(NULL === self::$_singletonFoo) { self::$_singletonFoo = new self::$_helperName; } return self::$_singletonFoo; } } </code></pre> <p>There's enough room for improvement. It's just a PoC, use your imagination.</p> <p>Why do it like that? Well, most of the time the application won't be unit-tested, it will actually be run, <em>hopefully in a production environment</em>. The strength of PHP is its speed. PHP is NOT and never will be a "clean OOP language", like Java. </p> <p>Within an application, there is only one Application class and only one instance of each of its helpers, at most (as per lazy loading as above). Sure, <strong>singletons are bad, but then again, only if they don't adhere to the real world.</strong> In my example, they do.</p> <p>Stereotyped "rules" like "singletons are bad" are the source of evil, they're for lazy people not willing to think for themselves.</p> <p>Yeah, I know, the PHP manifesto is BAD, technically speaking. Yet it's a successful language, in its hackish way.</p> <h2>Addendum</h2> <p>One function style:</p> <pre><code>function app($class) { static $refs = array(); //&gt; Dependency injection in case of unit test if (is_object($class)) { $refs[get_class($class)] = $class; $class = get_class($class); } if (!isset($refs[$class])) $refs[$class] = new $class(); return $refs[$class]; } //&gt; usage: app('Logger')-&gt;doWhatever(); </code></pre>
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    1. POIn a PHP project, what patterns exist to store, access and organize helper objects?
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    1. COI downvoted the answer because I believe suggesting the singleton pattern to handle the problem goes against solid OOP principles.
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    2. CO@koen: what you're saying is true, generally speaking, BUT as far as I understood his problem, he's talking about helpers for the application, and within an application there's only one ... uhm, application.
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    3. CONote: what I've presented is not even a real singleton pattern. A singleton would allow only one instance of a class by defining the constructor as private. It is only a "global" variable available to all "Application" instances. That's why I think its valid does NOT disregard good OOP principles. Of course, as anything in the world, this "pattern" should not be overused either.
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